Clinical applications of positron emission tomography.

Positron emission tomography (PET) has been used extensively as a research tool in the investigation of human physiology and pathology for over a decade. By labelling suitable compounds (for example, glucose, amino acids, ammonia, DOPA or drugs) with positron emitting isotopes which are then administered in tracer amounts, the blood flow, metabolism and even the cell receptor or neurotransmitter distributions may be assessed in vivo. Advances in PET technology and experience now make PET a powerful clinical diagnostic tool, enabling investigation of disease at a molecular level, even in the absence of anatomical abnormalities apparent on computerised tomography (CT) or magnetic resonance imaging (MRI). Clinical PET is already utilised in the management of patients with epilepsy, cerebrovascular and cardiovascular disease, dementia and a wide variety of oncological applications. PET will become more widely available shortly in the UK, with the opening of centres such as the Guy's and St Thomas's Clinical PET Centre in 1992. It will therefore become increasingly important that clinicians are aware of those specific areas in which PET may be the investigation of choice to optimise patient diagnosis, treatment and/or follow-up. This review will endeavour to explain briefly the principles of the PET technique, and then outline those areas where PET has already had an impact on patient management in comparison with the more widely available diagnostic tests, finally outlining promising areas where PET may become more clinically useful in the future.